I've shot all three and will pitch in as well.
Preface things by stating I am not a top shooter in any of them and am taking weather conditions out of the equation.
Sporting clays/5 stand - too many 'gimmes'.
Most operators, especially the commercial as opposed to club-run, know that higher scores bring back more shooters than a championship course set-up and set their courses up accordingly.
Get to know the operators and they'll admit it.
Skeet- Repetitive targets.
All of your targets travel a known path. Every time. Hence, the smaller gauges in an attempt to create challenges for the better gunners.
Challenging? Yes. Creative? Not so much.
Trap- Now that's 'Golf with a gun'.
And for the simplest of reasons. Your next target's path is an unknown.
I acknowledge that the 'two hole' field was adopted to raise scores, and that you run into more inflexible shooters than at the other venues, but I find the mental challenge of trap to be the most rewarding.
I think that challenge for perfection between the ears accounts for lower turnouts with more going to the Sporting clays and it's more 'exciting' target presentation.
Fire away, JT